1. Field of the Invention
The present invention is directed to an improvement of a temperature-sensing type fluid fan coupling device for supplying the cooling air to an engine in an automobile by automatically controlling a blow-out cooling air quantity upon sensing variations in outside ambient temperature corresponding to a traveling condition in relation to revolutions of a fan for cooling the engine.
2. Description of the Prior Art
The following is a description of an arrangement of a conventional fan coupling device of this type. FIG. 9 shows the principal portion of the device. An outflow adjustment hole (25') bored in a partition hole (25) leads from an oil reserving chamber (26) to a torque transfer chamber (24). The hole (25') is shaped as a straight hole. The outflow adjustment hole (25') is closed by a valve member (28) when an outside temperature exceeds a set value. The valve member (28) acts to interlock with deformations of a temperature-sensing member which are concomitant with variations in temperature. This temperature-sensing member is attached to a front surface of a sealing enclosure box. For this purpose, a front surface of the valve member (28) which confronts the outflow adjustment hole is formed flat. A proximal end of the valve member is secured to the partition plate (25) with a rivet.
The prior art described above, however, presents the following problems. The flat underside of the valve member (28) directly contacts the surface of the outflow adjustment hole (25'). Based on this engagement structure of the planes orthogonal to the biasing direction thereof, inconvenience is often caused in the contact engagement state. Besides, even when the valve member (28) separates slightly from the outflow adjustment hole (25') formed in the partition plate (25), an area of oil passageway in the hole (25'), as illustrated in FIG. 10(B), largely varies as compared with a rate at which the valve member (28) separates therefrom. This results in generation of large transfer torque due to a good deal of oil flowing via the hole (25') into the torque transfer chamber (24). This in turn causes a large increase in the number of revolutions of the fan. The power absorbed largely fluctuates, thereby causing a loss of power. The fan grows in noise, and further a supercooling phenomenon is developed.